A conventional conveyor diagnostic device as a first example has an acceleration sensor attached to a back side of a specific step, of a conveyor constituted by a plurality of steps coupled in an endless manner, in a direction to obtain sensitivity in a vertical direction. The conveyor diagnostic device as the first example acquires vibration data from the acceleration sensor and corresponding measurement times. Based on the acquired vibration data, the conveyor diagnostic device as the first example sets, as a reference time, a time when the specific step passes through a conveyor turnaround section at which plus or minus of an acceleration reverses, and compares vibration data from the acceleration sensor during the circulatory movement of the conveyor with vibration data during normal operation. Upon determining that there is an abnormal vibration, the conveyor diagnostic device as the first example measures an elapsed time from the reference time, and specifies an abnormality occurrence position (e.g., Japanese Patent No. 4020204).
A conventional conveyor diagnostic device as a second example has two acceleration sensors attached to a middle portion of a back side of a specific step, of steps coupled in an endless manner, to detect accelerations in a lateral widthwise direction and a horizontal movement direction. Accelerations detected by these acceleration sensors are sent to a signal processor. The signal processor includes a step position specifying unit, to specify, from outputs from the acceleration sensors, a passenger carrying/movement section, a turnaround section in which no passenger is mounted, and a deadhead section from the turnaround section to the passenger carrying/movement section. The signal processor includes an abnormality detection unit to detect an abnormality in the acceleration acting on the conveyor, based on outputs from the step position specifying unit and the acceleration sensors (e.g., Japanese Patent No. 4305342).
A conventional conveyor diagnostic device as a third example has an acceleration sensor and microphone attached to a middle portion of a back side of a specific step of steps coupled in an endless manner. The conveyor diagnostic device as the third example converts vibration signals and sound signals obtained from the acceleration sensor and the microphone into digital data, and stores the digital data in an information storage device. A processor specifies outward and return sections from the stored vibration signals. Based on the specified outward section/return section information, the processor extracts an average amplitude, kurtosis, and periodic component of the stored vibration and sound signals as statistical feature amounts, compares the statistical feature amounts with preset feature amounts, and determines a presence/absence of an abnormality in the conveyor (for example, Jpn. Pat. Appln. KOKAI Publication No. 2007-8709).
The conventional conveyor diagnostic devices as the first to third examples described above each are attached with an acceleration sensor or sensors and specify an abnormality occurrence position by using the vibration signal or signals obtained from the acceleration sensor or sensors.
According to the conventional techniques as the first and second examples, Relationships between elapsed times after identification of a conveyor turnaround section and step positions is set in a table in advance. Upon determining the presence of an abnormal vibration from vibration data of the acceleration sensor, each devices refers to the table to specify an abnormality occurrence position on the conveyor from the elapsed time after identification of a conveyor turnaround section.
In this manner, an abnormality occurrence position is specified from the elapsed time after identification of a conveyor turnaround section which is obtained from an output from the acceleration sensor. If, however, the step to which the acceleration sensor is attached passes near a conveyor turnaround section, passengers frequently ride on and off the conveyor. For this reason, low-frequency disturbance vibrations tend to occur.
As a result, low-frequency disturbances mix in a sensor output at the turnaround timing of the step to which the acceleration sensor is attached. This may lead to a reduction in the accuracy of turnaround identification and difficulty in identifying a turnaround.
In addition, when the conveyor runs at variable speeds or the running speed of the conveyor changes due to a failure in a conveyor driving unit, using the conventional techniques as the first to third examples may lead to a great reduction in the accuracy of specifying an abnormality occurrence position. Furthermore, the third conventional example is configured to specify the outward and return sections of the conveyor based on the identification timing of a conveyor turnaround section. If, however, the conveyor is long, an error in specifying an abnormality occurrence position may increase.